The present invention relates to an air spring arrangement having at least one integrated control valve for the admission of compressed air into a pressure chamber formed between an outer tube, a rolling tube and an air spring bellows which connects the outer tube and rolling tube, where the control valve can be actuated, with multiple switching positions, by integrated mechanical actuation means in a manner dependent on an air spring stroke for ride-height adjustment, where furthermore, the pressure chamber includes a compression spring which is braced at the face sides between a tube upper part of the outer tube and a tube lower part of the outer tube.
The field of use of the invention extends primarily to automotive engineering. In the area of the running gear of utility vehicles, for example, use is made of vibration dampers which include a normally hydraulic damping element and an air spring arrangement which interacts therewith. For an integrated design, the damping element normally has a reservoir tube which is connected to a rolling tube of the air spring, where the rolling tube is connected via an air spring bellows, which acts as a rolling bellows, to a concentric outer tube which is arranged so as to be axially movable relative to the rolling tube. The air spring bellows, the rolling tube and the outer tube delimit a pressure chamber which is charged with air pressure in order to realize the suspension action.
Vibration dampers of this type are fitted for example in the suspension arrangement of a driver's cab on a running gear of a utility vehicle, in order that the driver's cab is substantially isolated from the vibrations introduced into the running gear from the road via the wheel suspension.
DE 44 09 252 has disclosed an air spring arrangement for a utility vehicle, within which air spring arrangement there is arranged a control valve for the supply and discharge of compressed air, which control valve can be actuated, in a manner dependent on the ride height, by mechanical actuation means which are likewise arranged within the air spring arrangement. It is normally the case that, when the air spring falls to a minimum ride height, compressed air is supplied to the pressure chamber of the air spring arrangement in order to restore the suspension characteristics. By contrast, the pressure chamber is deaerated when it is sought to reduce the ride height of the air spring arrangement.
For this purpose, in this prior art, the control valve is composed of two individual valves, one of which is arranged on the outer tube and one of which is arranged on the rolling tube, which is movable relative to the outer tube. The actuation means are composed of a semirigid regulating rod by means of which the two individual valves are actuated alternately such that one individual valve is closed when the other individual valve opens. However, the actuation means appear to be highly cumbersome owing to the extremely large longitudinal extent and the very large number of individual components.
DE 102 00 553 C1 has disclosed a different air spring arrangement in which use is made of a single control valve which realizes not only aeration and deaeration of the internal pressure chamber but also a middle shut-off position. The control valve is actuated by likewise integrated actuation means which engage on one of the two air spring assemblies, outer tube and rolling tube, which are movable relative to one another. In this case, the actuation means have a structural length shorter than the stroke length of the air spring arrangement. A control element is preloaded by a spring against one of the air spring assemblies which are movable relative to one another, where the control element is mounted in floating fashion relative to the air spring assemblies. A second spring whose force direction acts counter to the first spring thus co-determines the position of the control element.
Furthermore, DE 10 2010 012 346 A1 has disclosed an air spring arrangement having at least one integrated control valve for the admission of compressed air into a pressure chamber formed between an outer tube, a rolling tube and an air spring bellows which connects the outer tube and rolling tube. The control valve can be actuated, with multiple switching positions, by likewise integrated mechanical actuation means in a manner dependent on the air spring stroke for ride-height adjustment. The mechanical actuation means comprise a compression spring which is fastened at the face side to the outer tube or rolling tube, the end of which compression spring interacts with an actuation plunger of a control valve arranged opposite on the rolling tube or outer tube respectively.
Furthermore, DE 196 49 316 A1 has disclosed a ride-height control system for vehicles having a lock chamber, having a lock inlet and having a lock outlet for the feed and discharge of fluid. Furthermore, the ride-height control system has spring elements, where a spring piston emerges from a working cylinder and displaces fluid counter to the pressure of a spring gas cushion. The ride-height control system likewise comprises a regulating opening which defines a setpoint ride height, a spring-compression range and a spring-extension range and which is shut off in the spring-compression range. Via a supply line, fluid is fed into the lock chamber in a feed phase and is discharged from the lock chamber in a discharge phase. The attainment of the setpoint ride height is registered and influenced by means of a sensor. As sensors, use may be made in particular of pressure sensors, or else of light barriers or a control tube fastened to the spring piston. Furthermore, the control tube may also be fastened to the working cylinder.
It is therefore an object of the present invention to provide an air spring arrangement whose control valve can be activated in a precise manner by robust and compact mechanical actuation means and realizes a stepped characteristic of the aeration and deaeration of a pressure chamber.
According to the invention, a lever which is mechanically connected to the at least one integrated control valve can be actuated, by at least one actuating lug arranged on a face surface of the tube lower part, in order to realize a stepped characteristic of an aeration and deaeration of the pressure chamber. The at least one actuating lug is preferably arranged centrally on the face surface of the tube lower part. The lever is mounted on a valve housing of the at least one integrated control valve. Both the lever and the at least one actuating lug are produced from a metallic material.
It is particularly preferable if the at least one integrated control valve is in the form of a 3/3 directional valve and aerates, deaerates and shuts off the pressure chamber. By the 3/3 directional valve, the three switching functions can not only be realized in a compact construction but can also be regulated in a precise manner.
The invention encompasses the technical teaching that the at least one actuating lug protrudes partially into the rolling tube in order to actuate the lever. An actuation of the lever leads to an actuation of the at least one integrated control valve, and to the associated functions of aeration, deaeration and shutting-off of the pressure chamber.
In a preferred exemplary embodiment, the at least one actuating lug is connected to the face surface of the tube lower part by way of a non-positively locking or cohesive connection. A screw connection or welded connection is particularly advantageous. The screw connection has the advantage of enabling the at least one actuating lug to be easily exchanged.
In a further preferred exemplary embodiment, the tube lower part and the at least one actuating lug arranged thereon are formed in one piece. The at least one actuating lug can thus be produced directly during the primary forming or deformation of the tube lower part.
It is preferably the case that the lever has a horseshoe shape and is mounted by way of the two distal ends on the valve housing of the at least one integrated control valve. The horseshoe shape is mounted on the valve housing at two locations, resulting in high stability and strength.
In a further exemplary embodiment, the lever has the shape of a bar and is mounted by way of one distal end on the valve housing of the at least one integrated control valve. This design of the lever yields a weight optimization owing to the material saving, where the reduction of the dynamic mass yields further advantages. Such advantages may include smaller spring elements and a more precise response behavior of the at least one integrated control valve.
It is furthermore provided that, between a full spring-extension position and a partial spring-extension position of at least +15 mm, the at least one actuating lug is not in contact with the lever and the at least one integrated control valve deaerates the pressure chamber, where a deaeration cross section decreases with progressive spring-compression travel.
The invention encompasses the technical teaching that the at least one integrated control valve imparts a shutting-off action in a spring-compression travel range between +3 mm and −3 mm.
It is furthermore preferably the case that aeration of the pressure chamber by the at least one integrated control valve requires a spring-compression travel of less than −3 mm, where an aeration cross section increases with progressive spring-compression travel.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
Further measures which improve the invention will be presented in more detail below together with the description of a preferred exemplary embodiment of the invention on the basis of the figures.